Milk Fertilizer: Fact or Fiction?

MILK FERTILIZER

Does milk really work as a fertilizer for plants and gardens?

Oh boy, I’ve seen this one pop up a lot lately, especially on social media ads for particularly terrible plant “care” apps and I’m like #WhatTheHalleck

I’ve also seen a ton of blog posts, mostly from natural or organic gardening sites purporting the “amazing” benefits of adding milk to your houseplants and garden plants. Always be sure to review scientific literature before you take these recommendations as valid. There was some faulty and statistics in earlier 2000’s on mild fertilizer, and some follow up research that showed no meaningful benefits. You can do your googling.

Plant peeps, please do not bother wasting perfectly good and expensive milk on your plants and garden.

1. Milk is not a “fertilizer”. Not by my definition. You expect a “fertilizer” to provide visible meaningful improvements in plant greening, growth, flowering, fruit production, correct? Well, dumping any undecomposed organic matter onto your plants isn’t going to give you that ROI. Any possible benefits are pretty meager at best. Milk is about 0.5% nitrogen, and 90% of milk is water. And no raw milk isn’t any better than pasteurized milk in this regard, as heat treatment actually breaks down milk molecules.
   
   
2. Yes, milk is organic matter. ANY organic matter you put into your garden or into potted plants can eventually break down (by heat/microbes) into the individual nutrients and compounds uptakable by plants. Adding fresh organic matter to your potted plants usually just results in a bunch of mold, fungus gnats, roaches, you name it.
   
   
3. Milk is WAY more expensive that buying more available nitrogen/other macros in the form of composted manure (or any other actual fertilizer). Like hundreds of dollars per kg of nitrogen, versus a few bucks per kg of nitrogen for the latter.
   
   
4. There is some research that milk can suppress powdery mildew…50–70% as effective at preventing pm, and about 40-50% as effective at reducing harvest loss as chem applications…but that’s from one study. But are you really going to waste milk on plant leaves when you could use some basic horticultural soap?
   
   
5. Got spoiled milk? Absolutely, don’t waste it. You can dump that in OUTDOOR soil or into the compost pile. Just like any other kitchen scraps, food waste, banana peels, etc. put it in the compost.